56 BULLETIN OF THE 



metre-killogranimes as his capacity for daily mechanical work. 9 

 Nevertheless these figures are after all only probable approxima- 

 tions, and there still exists, with regard to these questions, a large 

 and inviting field for the application of chemical and physical 

 methods to physiological research. 



All the mechanical work done by living beings is effected by 

 means of certain contractions of their soft tissues. The movements 

 of the amoeba, so often described of late years, may be taken as the 

 type of the simplest form of these contractions. Similar move- 

 ments occur, with more or less activity, in the protoplasm of all 

 young cells, and in the higher animals are strikingly illustrated by 

 the movements of the white corpuscles of the blood and the wan- 

 dering cells of the connective tissue. In the lowest animal forms 

 these simple amoeboid movements of the protoplasm are the only 

 movements, but in the higher forms, besides these, certain special 

 contractile tissues make their appearance, by which the chief part 

 of the mechanical work done is effected ; these are the striated and 

 unstriated muscular fibres. 



On account of the extreme minuteness of the little protoplasmic 

 bodies in which the amoeboid movements are manifested, the inves- 

 tigation of the mechanical means by which these movements are 

 effected has not as yet been attempted, although a great mass of 

 details have been accumulated by actual observation with regard to 

 the phenomena themselves and the conditions under which they 

 occur. Very little more has been done with regard to the con- 

 tractions of the unstriated muscular fibres. The striated muscles, 

 however, have been made the subject of a host of researches, and 

 I suppose the conclusions to which we may ultimately be led by 

 these can be regarded, with but little reservation, as applicable to 

 the function of the unstriated muscles, and also to the simpler 

 amoeboid protoplasmic contractions. 



Yet, notwithstanding the vast amount of experimental labor and 

 speculative ingenuity that has been lavished, since the time of Hal. 

 ler, upon the question of the contraction of the striated muscle, it 

 must be confessed in the honest language of Hermann, 10 that 

 the problem still mocks our best endeavors. For myself, I am un- 

 willing to believe that the phenomena of muscular contraction, or 

 indeed, of any of the varieties of protoplasmic contraction by which 

 animals effect mechanical work, will not by and by be fully and satis- 

 factorily explained on chemico-physical principles. I cannot for a 



